Computers, televisions, telephones and other electronic product contain large numbers of essential electronic semiconductor devices. To produce electronic products, hundreds or thousands of semiconductor devices are manufactured in a very small space, using lithography techniques on semiconductor substrates, such as on silicon wafers. Due to the extremely small dimensions involved in manufacturing semiconductor devices, contaminants on the semiconductor substrate material, such as particles of dust, dirt, paint, metal, etc. lead to defects in the end products.
Existing automated semiconductor processing system use robots, carriers, rotors, and other devices, to move and process wafers. These systems are designed to avoid creating particles which may contaminate the wafers. However, even with careful design, material selection, and system operation, particles may still be created by the moving parts of the systems, or by the contacting or abrasion of wafers by components of such systems.
Many automated semiconductor processing systems use centrifugal wafer processors, which spin the wafers at high speed, while spraying or otherwise applying process fluids and/or gases onto the wafers. The rotors typically hold a batch of wafers in a parallel array. While the close spacing of the wafers in such rotors has advantages, such as providing a compact design, if a single wafer breaks while within the rotor, the wafer pieces will often damage adjacent wafers.
During centrifugal processing of wafers within a rotor, it is important to have the process liquids contact the wafer surfaces in a substantially uniform way, so that all useable surfaces of the wafers receive substantially consistent processing, and so that all wafers within the batch of wafers in the rotor (as well as subsequent batches) are generally uniformly processed. As a result, it is advantageous for the rotor in the process chamber (as well as any tray or carrier installed into the rotor) to have a structure which allows the process liquids and/or gases to be sprayed through and onto the wafers. On the other hand, the wafers must be adequately supported to avoid excessive stress and wafer breakage so that the rotor must have adequate structural elements. In addition, as the rotor is typically cantilevered on a shaft extending from the back end of the centrifugal process chamber, and because the rotor may be exposed to large centrifugal forces when spinning at high speed, while remaining substantially centrifugally balanced, the rotor must be relatively rigid and strong. These requirements present design engineering challenges, as the increased material mass and thicker wall sections often used to achieve a strong and rigid design also tend to provide a more closed rotor structure, tending to limit the inflow/inspray of process fluids or gases.
Accordingly, there is a need for improved apparatus and methods for handling and processing wafers.
In a first aspect of the invention, an automated semiconductor wafer processing system has a carrier having wafer slots for holding wafers. The carrier preferably has tapered outside walls. A rotor in a centrifugal wafer processor has inner walls having a corresponding taper. The carrier is secured within the rotor, with minimum space requirements. Alternatively, the carrier preferably has step ribs and or lug ribs having a plurality of incrementally stepped carrier diameter surfaces. The rotor has corresponding incrementally stepped rotor diameter surfaces adapted to engage the carrier surfaces, when the carrier is installed into the rotor.
In a second and separate aspect of the invention, the carrier has a large number of comb slots extending circumferentially between ribs. The comb slots provide an open yet strong and rigid structure. Process chemicals and gases can pass through the rotor to reach the wafers within the rotor.
In a third and separate aspect of the invention, the comb slots are aligned or centered over the wafers. This allows a spray of process liquids to travel straight from spray nozzles to the wafers.
Other advantages will appear. The invention resides not only in the systems (and methods), but also in the subsystems and sub-combinations described and illustrated. The features shown with one embodiment may also be used with other embodiments.